PC experts come here.

but what is bothering me is the 120 fps on med settings

And im here happy with my 90 fps in low-med settings.

We have the same graphics card.
I mean, it's a good graphics card and you can pretty much play any game, but don't except to run games on high/ultra. Medium settings for most AAA games will get you around.

8gb of ram should help

Does your monitor even support such a high FPS?

GTX750Ti is good but its been beat up by GTX950 , another budget mid range card

Download more RAM.

For GTA V freezes I'm afraid that you're going to need more RAM, buying additional 4 GB would help you greatly, those freezes are a known issue to PCs with 4 GB RAM, as for the CS:GO I'm not really sure about that to be honest.

EDIT: Also your monitor is 75 Hz, meaning you can notice max 75 FPS on your screen, therefore not having above 120 FPS shouldn't really worry you unless you have a better monitor mate.

750Ti isn't a strong or high-end card. It's merely a mid range card so FPS in CS GO is normal. GTA V issues are probably you running out of RAM. But it could also be a CPU-based problem, install CPU-Z and check your clock speeds while gaming, if it changes while gaming something is wrong. Either way you need to upgrade your ram asap.

128 bit bus, 1gb vram?, 4gb ram are ur troubles
why didnt buy an amd videocard?

Out of range errors with monitors that are not 60 or 144 Hz Gsync can happen with NVidia frequently, especially if the game engine itself is expecting 60 Hz. A lot of engines tie calculations to frames, and they limit themselves to 60. So if the monitor is set to 75 Hz and the engine wants to initialise in 60, it can lead to strange things.

The 1-second hiccup is what was said before: you are out of memory and the game unloads unneeded data to load in the fresh. 8 GB nowadays is bare minimum for playing. Frankly, for anything slowly, the way browsers keep increasing their memory footprint.

i get over 120 fps on cs go withan ati hd 4600, 8gb ram and an i3 3.9 ghz... so ram will help you alot. yes my card is shit im buying a gtx 660 in februray

you can try a clean install of drivers using display driver uninstall, I don't know what could cause that :o

120 fps on med settings and 1124 resolution

75Hz

You running a weird CRT or something? Also I don't know what's the problem if you're running 120fps on a 75Hz monitor.

CS:GO is now heavily CPU-limited. I used to get 500FPS on an empty Dust2 a couple years ago with a 2500K CPU running at 4.2GHz and a GTX 780. Now, I get 300FPS with the same CPU and a GTX 980 Ti.

After every CS:GO update, it gets worse and worse. It puts more and more load on the CPU.

8-12GB of RAM would help for most games.

As for CS:GO, that is a very CPU intensive game as some other people have said. Your FX-6300 is for sure the problem here. The best bet would be a Z97 motherboard and at least an i5-4690k to get good fps.